1. Field of the Invention
The present invention relates to a printing apparatus and methods for controlling initialization process(es) carried out by the printing apparatus. More particularly, the present invention relates to a printer and methods that select one or more particular printer initialization processes to be performed according to the time difference between the leading and trailing edges of the pulse of a reset signal sent from a host computer. The present invention further relates to a software program for implementing the methods and media on which the program is recorded or carried.
2. Description of the Related Art
A printer that performs a process initializing its printing mechanism when a reset signal is received from a host computer and methods for resetting such a printer are generally known. A printer that performs an initialization process every time it is switched on is also known.
A typical printer initialization process includes the following:
(a) adjusting the phase timing of the stepping motor for driving the print head in the print line direction;
(b) positioning the print head based on a reference position;
(c) cleaning the print head;
(d) initializing a command buffer and other memory areas; and
(e) initializing certain printer settings, such as the form selection (slip or receipt forms, for example), font selection, print format (including character and line spacing), and printing mode (i.e., fine or normal).
Some of these initialization process steps require more time than others. For example, phase adjustment of the stepping motor (ensuring that a predetermined phase is excited) requires relatively little time, while print head positioning (synchronizing the actual position of the print head with data in a controller representing the position of the print head) and print head cleaning require more time.
The cleaning of the print head of an ink jet printer may be accomplished by drawing ink from the head and/or discharging it. In addition to being somewhat time consuming, this process also consumes ink. It is therefore desirable to avoid unnecessary cleaning operations as much as possible.
Conventional printers typically generate an interrupt at the leading edge of a reset signal, and perform all initialization processes at the trailing edge of the reset signal. Moreover, some applications that run on a host computer also send a reset signal to the printer every time the application starts up or at every printing transaction, thereby causing the printer to completely reinitialize at the end of every printing transaction. One problem with this arrangement is that it results in the execution of unnecessary initialization processes which, in turn, unnecessarily depletes the supply of consumables such as ink and also reduces printer throughput.
Consider, by way of example, a conventional point-of-sale (POS) system which runs a common application that sends a reset signal with every print transaction. With this arrangement, the print head cleaning operation is performed with every print transaction, thus consuming a large amount of ink. This greatly increases operating costs, and reduces the processing speed of each print transaction because of the lengthy period of time required for the initialization process.
It is therefore an object of the present invention to overcome the aforementioned problems.
In consideration of the above-described problems, another object of the present invention is to provide a printing apparatus and a method therefor that can select the appropriate initialization process(es) according to the time duration of a reset signal sent and also according to the needs of the host computer.
A further object of the present invention is to provide a program of instructions (i.e., software) for implementing the control methods of the invention and media on which the program is recorded or carried.
To achieve the above objects, a printing apparatus having a printing mechanism for printing text or graphics based on commands and print data received from a host device is provided. According to one aspect of the present invention, the printing apparatus comprises a controller that controls operation of the printing apparatus, an interface circuit adapted to receive a reset signal from the host device and transmit the reset signal to the controller, and a timer circuit that measures the duration of each of the reset signals received by the controller. The controller selects which one, if any, of a plurality of initialization processes is to be performed based on the duration of a respective reset signal.
Thus, a printer according to the present invention can select a specific initialization process according to the duration of a reset signal sent from a host device, where the duration is the time period between the leading and trailing edges of the reset signal. This enables the printer to perform an appropriate initialization and reset process given the present operating conditions.
The printing apparatus preferably comprises a comparator that compares the duration with at least one specific threshold time. In this case, the controller either determines that no initialization process is necessary or selects and causes one or more specific initialization processes to be performed based on the result of the comparison by the comparator.
Preferably, the controller causes a first initialization process to be performed when the duration is less than a first specific threshold time and causes a second initialization process to be performed when the duration is greater than or equal to the first specific threshold time.
Thus, in accordance with the present invention, because each specific initialization process need not be performed each time the printing apparatus receives a reset signal, printing throughput can be improved.
Preferably, the printing mechanism comprises a stepping motor, and the first initialization process includes a process for adjusting the phase of the stepping motor. When the printing mechanism comprises a print head, the first initialization process also preferably includes a process for synchronizing the actual position of the print head with data in the controller representing the position the position of the print head.
The printing apparatus further preferably comprises memory for storing at least one among various printing apparatus settings, a command from the host device, or print data. In this case, the first initialization process includes a process for clearing part or all of the memory.
When the print head is an ink jet type, the second initialization process preferably includes a process for cleaning the print head. In this case, the present invention can significantly reduce ink consumption by performing time consuming print head cleaning only when needed.
Preferably, the timer circuit comprises a real-time clock that measures time, and a delay circuit that delays the reset signal output from the interface circuit for a specific time and supplies the delayed reset signal to the controller. The controller performs the selected initialization process, which is one out of the plurality of initialization processes selected according to the duration, in response to the delayed reset signal.
According to another aspect of the present invention, the comparator compares the duration with two different threshold times (i.e., first and second specific threshold times). Based on this comparison, the controller causes a third initialization process to be performed when the duration (t) is less than the second specific threshold time (t1), causes the first initialization process to be performed when the duration is greater than or equal to the second specific threshold time and less than the first specific threshold time (t2), and causes the second initialization process to be performed when the duration is greater than or equal to the first specific threshold time.
The printing apparatus further preferably comprises memory for storing at least one among various printing apparatus settings, a command from the host device, or print data. In this case, the third initialization process includes a process for clearing part or all of the memory.
Also, in one embodiment using two different threshold times, the first initialization process may include processes for clearing part or all of the memory, adjusting the phase of the stepping motor, and synchronizing the print head; and the second initialization process may include these processes plus a process for cleaning the print head.
The present invention may also be embodied as a method of controlling a printing apparatus and in particular for selecting one or more specific initialization processes to be performed based on the reset time of a reset signal received by the printing apparatus from a host device. Such a control method, when carried out, achieves the same benefits as described above.
Such a control method may be implemented by a program of instructions (i.e., software) which may be embodied on a device-readable medium. The instructions may be supplied to the printing apparatus for execution by the controller. The device readable medium on which such a control program is recorded can be distributed or marketed as a software product separate from the printer with which the program is used. Running such a control program on a printer yields the abovedescribed benefits of the invention.
Some exemplary device readable media for storing the control program of the invention include CD-ROMs, floppy disks, hard disks, magneto-optical disks, DVD (digital video disk or digital versatile disk) media, semiconductor memories, and magnetic tape. Any of these or other suitable storage media can be used to introduce the control program of the invention to existing printing apparatuses.
Device readable media may also include a carrier wave in which the control program is embodied. In this form the control program can be transmitted via the Internet or other computer network from a remote location to a location where the printing apparatus resides for use by that printing apparatus. It is also possible to place this control program on a World Wide Web (WWW) site on the Internet so that users can download the program for introduction to and use with an existing printer. These and other variations are included within the scope of the present invention.
Other objects and attainments together with a fuller understanding of the invention will become apparent and appreciated by referring to the following description and claims taken in conjunction with the accompanying drawings.